In the past, compound bows have used two cams, respectively mounted on the limb tips of opposite ends of the bow, to provide the means to store more energy in the draw cycle and to reduce the holding force at full draw. These eccentric cam elements must be accurately synchronized with respect to the radii of eccentricity so that the rate of feed-out will be approximately equal at both ends of the bows. This requires synchronized indexing of the two cams when the cams and cable elements are being assembled. Such a double cam compound bow construction is illustrated by the bows disclosed in the following prior art patents.
______________________________________ U.S. Pat. No. Issued To Date Issued ______________________________________ 3,486,495 Allen Dec. 30, 1969 3,890,951 Jennings, et al June 24, 1975 4,060,066 Kudlacek Nov. 29, 1977 4,079,723 Darlington March 21, 1978 4,112,909 Caldwell Sept. 12, 1978 4,300,521 Schmitt Nov. 17, 1981 ______________________________________
The early compound bows utilized cams consisting of eccentrically mounted circular shaped elements. As the desire for more stored energy and greater arrow velocities developed, special shaped cam elements were designed to provide these characteristics. These shaped cam elements, like the circular shaped elements, were mounted on the limb tips. It is well known in the art that to obtain the best bow performance, the cam elements at each end of the bow should be properly synchronized with each other. Patents disclosing various means to accomplish proper cam synchronization include the following:
______________________________________ U.S. Pat. No. Issued To Date Issued ______________________________________ 3,841,295 Hunter Oct. 15, 1974 3,958,551 Ketchum May 25, 1976 4,103,667 Shepley, Jr. Aug. 1, 1978 4,178,965 Groner Dec. 18, 1979 ______________________________________
The more modern compound bows have reverted back to the more simplistic design of the original U.S. Pat. No. 3,486,495 Allen patent, but the requirement for cam synchronization is still present as noted, for example, by the teachings of the following patents:
______________________________________ U.S. Pat. No. Issued To Date Issued ______________________________________ 4,372,285 Simonds Feb. 8, 1983 4,440,142 Simonds Apr. 3, 1984 4,909,231 Larson Mar. 20, 1990 ______________________________________
It is obvious, of course, that the use of a single cam avoids the problem of cam synchronization and, in fact, there are single cam bows known in the prior art. One such bow, popularly referred to as the "DynaBo" was invented by Len Subber. The original Dynabo design had one working limb located at the upper end of the bow handle. A single cam element was mounted on a rigid pylon at the lower end of the bow. The single cam element functioned in the same manner as the cam elements on the previously mentioned two cam bows. As the Dynabo was drawn, one track of the cam element payed out line to the bowstring which was fixed to the upper limb tip and the other track on the cam element acted as a take-up reel for a second line that was also anchored at the tip of the upper working limb.
Since there was only a single cam element, there was not a synchronization problem between two cams. There was, however, a problem in synchronizing the rate that the cam fed out cables to the bowstring at the lower end of the bow and the rate that the flexing of the upper limb fed out cable to the bowstring at the upper end as the bow was drawn. The result was a rather unpleasant feel to the bow as it was drawn and there was a drastic movement of the nocking point and the rear end of the arrow as the bow was drawn and released. This, in turn, made it very difficult to achieve good arrow flight from the bow under normal conditions. An early version of the DynaBo was described in the September 1976 edition of "Archery World" beginning at page 28.
The Dynabo single cam concept was offered in at least three different versions from as many manufacturers during the 1970's, and at least one manufacturer, Graham's Custom Bows, employed the Dynabo concept, with two working limbs. A description of the Graham bow is contained in the June/July edition of "Archery World" magazine. The Dynabo bow, however, never did become an acceptable alternative to the two cam bows and, in fact, appears to have lost whatever popularity it had achieved by the late 1970's.
Another known prior art device that had the capability of providing a solution to the previously mentioned problems of cam synchronization and synchronized bow string feed out (the latter being desirable to enable the nock end of the arrow to travel in a smooth, consistent path upon draw and release of the arrow) is set forth in U.S. Pat. No. 4,562,824 issued to Jennings. This patent teaches the use of a single multiple grooved cam mounted on a pylon attached to the bow handle. The cam had one string track feeding cable attached to an idler pulley mounted in the limb tip at one end of the bow and a second track feeding line to a second idler pulley mounted in the second limb tip at the other end of the bow. The cam also has two additional tracks, each of which take up line while the string tracks feed out line to the bow string. One take-up track is taking up a line which is anchored at one limb tip while the other take-up track is taking up a line which is anchored at the opposite limb tip. Thus, the '824 patent teaches a highly complicated system, as compared to the present invention, that is composed of considerably more parts resulting in a compound bow having greater mass weight than the more conventional two cam compound bow.
A single cam bow developed by Larry D. Miller in the late 1970's or early 1980's was the subject of a U.S. patent application titled "Archery Bow Assembly" (hereinafter referred to as the "Miller application"). The Miller application discloses the use of a single pulley, having two grooves thereon for feeding out line to the bow string. The primary groove is circular and concentric with the axle of the circular pulley. The secondary groove, also circular, may be slightly eccentric for the purpose of maintaining the nocking point of the bowstring perpendicular to the handle section of the bow. A third eccentric groove carries a take-up cable to provide the entire means of compounding (i.e. achieving the desired reduction in holding weight at full draw and storage of energy).
The Miller application, the serial number of which is not known, may be considered material to the examination of the subject application.